Screen magnifiers are a type of assistive technology used by visually impaired people with some functional vision. By magnifying areas of the screen, the screen magnifier allows people that would otherwise not be able to see areas of the screen that are too small to enlarge these areas. Screen magnifiers are software applications that present a computer's graphical output in an enlarged form. Many screen magnifiers act similar to a physical magnifying glass that a user can move around over the screen to magnify a specific area, except rather than a physical object the screen magnifier is software and the user moves the displayed glass or lens with the mouse or other input device. The most common method of magnification is to present an enlarged view of a portion of the original screen content that covers a portion of or the entire screen. The enlarged view often tracks the pointer or cursor as the user moves a mouse or other input device around the screen so that the user can magnify different areas. Screen magnifiers may work with a single application or across multiple applications at the operating system level. For example, Microsoft Windows Vista includes a magnifier application for magnifying the entire desktop and any applications displayed on it.
A screen magnifier can be presented as a window that, when placed over other windows or the desktop, magnifies the contents of other windows. For example, the magnifier may act as a lens that can be moved around (i.e., panning) to enlarge various areas of the screen. A screen magnifier can also be displayed full screen, so that it takes up the entire display. In this mode, the display only shows a portion of the actual screen at a time. For example, at a magnification factor of 4 times (4×), only one-eighth of the desktop can be shown in a full screen magnifier at a time. Thus, to see the other three-fourths of the desktop a user moves the magnified area around in a process called panning.
One goal of a screen magnifier is to enlarge toolbar and other buttons and controls so that a visually impaired user can interact with applications. This includes the screen magnifier application itself, which typically displays a user interface for controlling aspects of the magnifier. For example, the user may interact with the user interface to modify the zoom level or set whether the magnifier takes up the full screen or displays a magnified view in a window. The screen magnifier may include a user interface that the magnifier keeps within the view so that the controls of the user interface are available to the user at any time.
Unfortunately, in larger magnification contexts the UI becomes obtrusive, because it consumes a significant portion of the screen. Even a small toolbar can be quite large when the user views the toolbar at, for example, a 16× zoom level. Although this helps the user to be able to see the screen magnifier controls, the user may no longer be able to see other applications or enough of other applications to perform typical operations. For example, a user viewing a list of files in a file management application may not be able to see a file and a folder that the user wants to drag the file into at the same time because of the limited amount of screen real estate. Thus, the user may find the screen magnifier's own user interface frustrating. Some screen magnifiers solve this by removing the UI from the screen and providing key sequences that the user memorizes to display the UI again. This approach is not accessible to new or novice users unfamiliar with the keyboard shortcuts, and may make the screen magnifier less accessible to a broad audience.